Investigation of the chalcogen interdiffusion in CuIn(TeSe)2 thin films

Graded thin films of CuInSe₂ on CuInTe₂ have been obtained by annealing of precursor structures containing Se and Te separated in depth. The depth profile of the phases in the film was investigated using X-ray diffraction with grazing incidence of the primary beam. Quasi-epitaxial growth of CuInSe₂ on a CuInTe₂ film next to the Mo back-electrode was observed after annealing at 450°C in vacuum. Annealing at higher temperature lead to chalcogen interdiffusion resulting in quaternary films. However, heat treatments of already reacted films did not result in any detectable interdiffusion. From these results the mechanisms governing the growth of films from precursors containing the chalcogens Se and Te separated in depth are discussed with respect to their application for thin film solar cells.